It's tough dealing with dogs, especially more than one, because they can come at you from different sides simultaneously. I'm not an expert by any means, so you should definitely consult animal control/the local authorities by all means.
You can't outrun a dog (most dogs medium-sized or larger and in fair health). So, use several things to your advantage.
1) Size. You're probably bigger than the dog in stature, if not in weight. Hold your arms out, drape open your coat if you have one, anything to make yourself look bigger. This is a trick nature does all the time with feathers, fins, webbing, wattles, wings, fur, etc. Suddenly, what looks like it might have been a manageable size looks bigger. Dog has second thoughts. You hope. The only problem with this is, some breeds were specifically engineered to take down things that are much bigger (elk hounds, bull-baiting dogs, bear-baiting dogs, wolf-hounds etc.). Still, it can give the dog a moment to think.
2) Sound. Short, sharp, loud noises startle dogs and, if they have room to run, they may back off. Growl at the dog and let it know that you are aggressive and not happy. Some dogs may not want to fight something that fights back.
3) Arm yourself. A rock in the hand will give your punches more weight, and a stick can jab at eyes, throat, and belly, or be used to beat. I don't advocate violence against animals, but when it comes down to it, and the fighting starts, it's nature at its rawest form, and you better be willing to go all the way. Like Josey Wales says, "You got to get plum mad dog mean." No foolin'.
4) Position. Can you get to a height? If so, you have an advantage. If you climb a tree, you're cornered. Don't let the dogs corner you, they may never let you go (and as your wife noticed, motorists may not want to help, or stick around long). Try to find a place where they can't get at you from more than one side.
5) Preparedness. Always carry a cell phone and some form of chemical repellent. Learn how to use the repellent. Have it at the ready while walking. It doesn't do any good fumbling in your pocket while Fido is chomping. Be ready, though. Some chemicals just make animals angry. If you can wear protective clothing, the more layers you have, or thicker materials, will make it harder for dog teeth to find purchase. Nonetheless, dogs have very strong jaws (rottweilers probably exert huge amounts of pressure; I remember reading that gray wolves can exert 400 lbs. of pressure per square inch in their bite, and I wouldn't be surprised if many breeds of dogs are similarly strong; the Scottish terrier I grew up with could grip a rope and be lifted off the ground holding on only with her jaws; her bite was fierce)
6) Attitude. Get a mental attitude that's not letting the dogs show dominance. You can still be scared, but get mad, too. Show that you're aggressive with the noise I mentioned above, and by not running. Dogs are highly socialized to recognize pack dynamics, even if they've never had training. Dogs know when they see an alpha, and you have to show them you're the alpha, even if your mentally fleeing in terror. Look the dogs in the eye: for many humans, this is a challenge, but in the case of many dogs, it can mean you aren't gonna put up with their guff. If it comes down to a fight with the dog, hit it hard and fast and try to roll it over on its back, then hold it down and restrain across it's throat (in dominance establishment situations, many dogs will lock jaws over the throat of another dog, and a dog on its back shows submission). The dog may not stay down, but it may recognize that you're not a pushover, and try to get away. Dogs also tend to have highly developed senses of smell, and if you get your mad adrenaline working at least as hard as your fear adrenaline, you may begin producing pheromones that may say, "Get the hell away from me or you'll regret it," and the dog may react accordingly.
7) Awareness. Note the territory. Many dogs are o.k. with guarding their territory, and if you can leave (calmly, not running, which may invite pursuit) their territory (assuming it's obvious just what that territory is), they may back off. Keep your eyes on the dogs at all times. Know where your escape routes are, water sources, areas of high traffic, and dead ends are.
8) Tactics. If a fight starts, wound the dog severely. It's awful, but it has to be done. Eyes, throat, belly. Hitting a rottweiler anywhere other than a vulnerable throat or eyes is useless, as they're practically made of stone. Upend the dog and get it on its back as soon as possible (they fight better when all four legs are on the ground; don't give them that option).
9) Groups. Does your wife have someone she can train with? The bigger the pack, the less likely the dogs are to try anything.
10) Alternatives. Different route.
11) Civic action. Call the local authorities, even if your wife never walks that route again. They need to know that there are some bad dogs (or at least improperly leashed or contained dogs) around for the safety of others, including mail carriers, delivery people, local civic workers, area children, elderly, everyone.
Of course, none of this guarantees any certainty for protecting yourself or your wife or even success if the situation turns sour, as with animals, it's always unpredictable. I don't know if Kid Cthulhu drops by this section of the boards much, but I seem to recall her line of work involves serious dog training, and she probably has a lot better insights than mine.
Hope your wife is o.k. Take care.
Warrior Poet